From all of my experience, the two most common ways that a water pump fails is:
1. Seal fails, and leaks coolant out the "weep hole" on the bottom of the casting.
2. Bearings get "rough and noisy."
About #1, it will be obvious, because coolant will be leaking out.
About #2, it will be detectable by "the experienced ear."
-Also, about #2, I once saw a car ('63 409) with the fan blades stuck into the radiator when the water pump shaft broke. Evidently a result of a "seized bearing."
So, from my point of view, if I had a pump with a noisy bearing, I'd darn sure replace it. (granted, you won't have to worry about the fan blades into the radiator,,,,,)
Also, a word of caution: A rough bearing noise could be coming from several different places, and they all sound pretty much the same. If it were me, I think I'd remove the belt tension, slide the belt out of the way, and rotate (and/or spin) each device by hand, while "listening and feeling" for a rough bearing. CHECK ALL DEVICES, -including the tensioner pulley, any idler pulley if there is one, alternator, etc etc.
Dark Cherry 99 Bonneville SE -her car
Ivory 02 Bonneville SE -MY CAR !
"luxury with attitude"